Walking a Mile a Day Protects Brain from Effects of Aging

October 28, 2010

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Kirk I. Erickson, PhD, Assistant Professor in the Department of Psychology of the University of Pittsburgh discusses his paper “Physical activity predicts gray matter volume in late adulthood: The Cardiovascular Health Study” that was recently published in the Neurology® journal (2010;75:1415-22). He spoke with José Merino, MD, Science Editor of AAN.com.

AAN.com: Briefly summarize the methodology and major findings of your study.

Erickson: We collected information about the level of physical activity of almost 300 people who were between 60 and 65 years old. Nine years later we used MRI to look for evidence of brain atrophy and four years after the MRI we examined them for look for evidence of mild cognitive impairment of dementia. We found that people who were more physically active had more brain tissue nine years after the initial evaluation and a lower risk of developing cognitive impairment. These results are quite astonishing because for the first time we can say that the amount of physical activity in late adulthood is associated with long-term sparing of brain tissue.

AAN.com: In your study, what was the duration and intensity of the physical activity necessary to prevent gray matter volume loss?

Erickson: Participants were about 63 years of age when they enrolled in the study. Physical activity was protective: people who exercised had less atrophy nine years later. But this effect was only apparent in subjects who walked about 72 blocks or more per week at the time of the baseline evaluation. Seventy-two blocks are equivalent to 6 to 9 miles, depending on the city. This means that to have the protective effects of exercise on the brain, people in their early 60s need to walk about one mile per day. We do not know how much physical activity our subjects had before the baseline evaluation, so we cannot say whether physical activity earlier in life has these effects.

AAN.com: In your sample, did patients who walked the most blocks also engage in other forms of exercise or participate in other activities that may prevent or delay the onset of cognitive impairment?

Erickson: Physical activity is not the only behavior or lifestyle factor that influences our brain: diet, intellectual stimulation, and stress, for example, may also impact how our brain ages. In our study we controlled for many of these variables and were able to determine that physical activity affects the brain independently from other lifestyle habits, intellectual pursuits, and genetic risk factors for Alzheimer’s disease.

AAN.com: In addition to the distance people walk, does the intensity of the physical activity have an effect on the brain?

Erickson: In this sample we did not have sufficient information on the intensity of the exercise intensity to answer this question, but it is an important issue for future research. Other studies suggest that moderate intensity exercise is necessary to reap the benefits for your brain.

AAN.com: Does exercise early in life also have a protective effect?

Erickson: It is likely that greater amounts of physical activity influence the brain and cognition throughout the lifespan. In fact, several studies with children find that fitter children perform better on academic achievement tasks in school and have more brain tissue than their less fit counterparts. All of these results suggest that physical activity is a very powerful method to improve memory function throughout life.

AAN.com: Why do you think exercise prevents gray matter atrophy?

Erickson: We get a lot of our information about how this works from animal studies. Many studies in animals find that exercise increases the total number of cells in the brain, increases the amount of blood circulating to the brain, and increases the number of connections that the cells make to one another. This makes for a more efficient, more interconnected, and more nutrient rich environment, which results in improvements in learning and memory.

AAN.com: What is the relationship between gray matter atrophy, exercise, and cognitive impairment?

Erickson: We find that greater amounts of exercise leads to reduced gray matter atrophy and that a greater amount of gray matter reduces the risk for cognitive impairment.

AAN.com: What are the implications of your findings for clinicians?

Erickson: As we search for a "magic intervention" to protect our brains from the effects of aging, we may find that this "magic" will come not in the form of a pill, but rather in the form of a brisk walk several days a week. So, I would recommend physicians to prescribe moderate amounts of physical activity—about 1 mile of walking per day—to improve brain function, reduce brain atrophy, and decrease the risk for cognitive impairment. Aerobic activities, such as a brisk walk, a game of tennis, or a swim are excellent activities that may improve brain function.

Author Disclosure:

Dr. Erickson has received research support from the University of Illinois and the University of Pittsburgh.

Dr. Merino performed a one-time consultation with staff from Bell, Falla and Associates.

He is a member of the Stroke Publishing Technology Committee for the journal Stroke and was a member of the editorial board of Stroke from 2008-2010.

Dr. Merino has received research support from the cost reimbursement contract between NIH/NINDS Intramural Program and Suburban Hospital to support the clinical, administrative, and technical activities of the NIH Stroke Program at Suburban Hospital. He is also stroke adjudicator for the Women's Health Initiative at NIH.